Electrolytic apparatus for forming tire molds



May 5, 1942.

J. W. BISHOP ET AL ELECTROLYTIC APPARATUS FOR FORMING TIRE MOLDSOriginal Filed Aug. 51, 1957 2 Sheets-sheaf. l i

INVENTORS JflJfP/l #4 B/JHUP 457/905 M4 5011 M A ATI'O EYS May 5, 1942.J. w. BISHOP ETAL ELECTROLYTIC APPARATUS FOR FORMING TIRE MOLDS 2Sheets-Sheet 2 Original File d Aug. 31., 1957 INVENTORS dflrfif/ /v M5/6'170/ Air/swam 51/14 MA ATTORNEYS structing tire molds.

Patented. May 5, 1942 UNITE S'F'EES @ATENT OFFICE-v estatessmcrnorlr'rro srr'a'rns iron. roof was Moms Joseph W. Bishop, Detroit,and Arthur W. Bull, Grease llointo, Mich. assignors, by mesne assignments, to United States Rubber (Company, New liorh, N. X, acorporation oi New Jersey (l rigii appiication August 81, 1937, SerialNo. romeo. Divided and this application August 116, i932, FFeriai No.225,i2t

(or. zoo-21s;

This invention relates to molds, and in particular to molds forpneumatictires. More particularly, the invention relates to theformation of tire molds by'the electrolytic deposition of a ferrousmetal, being a divisional of application Serial No. 161,736, filedAugust 31, 1937. In general, the invention comprises the formation ofmolds the contour of which is determined by a matrix over which ametallic shell is formed primarily by electro-deposition, whiledeficiencies due to irregularities in plating are corrected by atomizedthermaldeposition of metal.

While the idea of forming molds by electrolytically depositing a shellof metal over nonmetallic and electrically non-conductive surfaces isnot new, use of this process as adapted to the construction of moldsemployed particularly in the manufacture of rubber tires has not beenconsidered commercially satisfactory. Prior processes have beenobjectionable due to the difficulty of commercially electro-depositing aferrous metal; one disadvantage among others being the diflicultyofmaintaining uniformity of thickness of e1ectro-deposited metal, since inthe process of electrolytically depositing a ferrous shell over acathode of intricate design metal sometimes forms in thick deposits onareas near an anode while other areas and obscure corners receive littleor no deposit of metal. The high cost of manufacture has also presenteda problem diflicult to overcome.

The process and apparatus of the present invention permits theproduction of a satisfactory tire mold by using a rubber form as amatrix on which an appropriate metal such as iron is deposited. Thus, inmanufacturing a plurality of similar molds the diihculty of manuallyengraving a design for each individual mold is obviated, resulting in aconsiderable saving in cost of manufacture over the conventional mode ofcon- Furthermore, molds pro- ,duced by our method are capable ofwithstanding constant daily use over as long a period as 7 matrixpermits the formation of homogeneous ous' electro-depositlon. Also, thecoordination of the two modes of applying metallic deposits to a sultingfrom the dual deposition method, in combination with comparatively lowcost.

These and other objects and advantageswill appear morefully in thefollowing detailed description when considered in connection with theaccompanying drawings, in which:

vFig. 1 is a vertical view, in section, of a transaxial portion of apneumatic tire mold;

Fig. 2 is a similar view showing a rubber matrix formed therein;

Fig.- 3 is a fragmentary view, in section, illus- I trating a completedmatrix? Fig. 4 is a vertical view, in section, illustrating a platingtank and cathode rotating mechanism associated therewith;

Fig. 5 is a vertical view, in section, taken on section line VV of Fig.4; with the cathode and attached mechanism in raised position;

Fig. 6 is a transaxial view of a matrix after a deposit of metal hasbeen applied thereto;

Fig. 7 is a transaxial view, in section, of a shell formed by depositedmetal; and

Fig. 8 is a transaxial view, in section of a tire mold constructed inaccordance with the principles of the invention.

With reference to the drawings, and in particular to Fig. l, we show atransaxial portion of a pneumatic tire mold of conventional construction comprising a single metal shell i. This part of the mold comprisesan exterior flat surface 2 and an opposing, substantially parallel,surface 3 adapted to contact and register with a correthat obtained bymolds of standard construction.

sponding side of a second transaxlal portion of a mold to form acomplete tire mold. A circular Y cavity 6 formed in the mold at thesurface 3 includes a pattern or design 5 which may be in the form of anydesired tread configuration used in pneumatic tires.

in order to produce a satisfactory matrix on which ferrous metal can bedeposited, with the accompanying minimum of shrinkage and de= formationof said matrix, it is preferable to employ a back plate 6 (Fig. 2)having an annular convex portion '5 integral therewith to support thecontour of the matrix. When the parts are positioned in relationshipwith each other, as shown in Fig. 2', the convex side of the back plateprojects into the mold cavity 4 and affords a stud 22 with the link 2|.

substantially uniform space between walls thereof and the adjacentsurface of the mold cavity. It it preferable to treat the convex sideoi? the back plate in any convenient manner that will assure effectivebonding'of rubber to metal, such as by first electroplating the convexside with brass.

A matrix is formed by vulcanizing rubber in bonded relation with theconvex side of the back plate 6, the exterior of the matrix assuming theconfiguration of the mold cavity. To effect this operation, uncuredcompounded rubber is cemented to the convex side of the back plate 6 oris placed in the mold cavity, the back plate and mold l are broughttogether under pressure, and the rubber is subjected to vulcanization.Upon disengagement of the plate from the mold, a matrix 8 has beenformed, with a contour adequately supported and assuming a transaxialreplica of a pneumatic tire. The matrix is made in transaxial formbecause it is customary to form tire molds in two separate units whichwhen assembled form a complete pneumatic tire mold split along thetransaxial plane.

An electrical insulation covering a of any suitable materlal such asrubber is applied to the exposed metal surface of the back plate 8, carebeing taken to leave areas it and II adjacent the rubber matrix exposed,as shown in Fig. 3, to afiord an electrically conductive surface to a,the matrix- In order to render the non-conducner, preferably-by boltsl3, l3, as shown in Fig. 5.

The spider, in turn, is secured to a spindle i l having sheaves l5 andI6 mounted at each end. lhe sheaves l5 and I6 engage with belts l'i and68, respectively, and by meansof the belts the weight of the spindle andattached parts is supported in a solution I 9 contained in a rubberllnedtank 20. One end of the shaft I4 engages with a connecting link 2|, bymeans of a stud screw 22, in a manner permitting attachment of the linkto the spindle, but allowing rotation of the Mounted at one side of thetank 20 and electrically insulated therefrom is an electrical terminal23 (Fig. i) which is connected to the link 2| by an arm 2%. A swiveljoint at each end of the arm 24 allows substantially vertical movementof the matrix, yet assures effective electrical conductivity between alead wire 25 and the surface of the matrix 8.

In order that current conducting parts such as the link 2!, screw 22,pulleys l5 and it,

spindle it, and spider l2 will afford no bare s'urfaces to attract adeposit of ferrous metal when immersed in the solution is, they arecovered with some'suitable insulation substance such as rubber, carebeing taken, of course, that adjacent contacting surfaces at the jointsremain free from the insulating material.

Adjacent one side of the tank 28 and opposite the matrix it a plate offerrous metal 25 (Figs. 4.- and 5) is suspended from a bus bar 217 bymeans of books The extremity of the bus bar passes beyond the exteriorof the tank and has mounted, at the end thereof, an electrical terminal29 to which a lead wire 30 is connected.

Although a number of ferrous plating solutions are well known in theelectro-deposition art, good utilized to elevate the cathode.

posed of 100 grams of ferrous chloride and 200 grams of calcium chlorideper liter of solution. Proper acidity of the solution may be effected bythe addition of suitable quantities of hydrochloric acid. In operationthe matrix functions as a cathode upon which metallic iron from thesolution is deposited. The plate 25 acts as the anode and. dissolves inthe solution, compensating for the loss of salts originally containedtherein.

'In order to avoid brittleness of the electroformed metal shell, it ispreferable to heat the solution. This is accomplished by providing aheating coil 3! which may be connected to a the anode have a greatertendency to accumulate electrolytic metal than have surrounding areas,and this property is further accentuated as a deposit thus formed growstoward the anode.

Rotation of the cathode is 'eiTected by a mechanism 32 mounted on aplatform 33 supported by upright posts 36 and 35 and obliquely disposedbraces 36 and 31. The lower extremities of the posts and braces aresecured to the tank 20 while the upper ends are joined together 'at apivot shaft 3% to which the platform. 33 is pivotally connected. Theplatform is free to swing upwardly but is limited in downward movementby a cross-rail member 39 affixed to the braces 36 and 31. A foot member40 attached to the base of the platform 33 is'adapted to contact withthe cross-rail 39. A motor mounted on the platform 33 imparts rotativemotion to the pulley 42 through a gear reduction unit 43, pulley 44, andbelt 45. The pulley 42 is keyed to a shaft 66 and drives pulleys H and48 also rigidly secured to said shaft. The weight of the cathodeassembly is sustained by the belts i1 and I8 passing over the pulleys 41and 48, respectively. Bearings 68 and 5d mounted on the platform 33support the shaft 46. By this disposition of driving means the cathodeis rotated about its axis during deposition.

It is well known in the electro-plating art that the more remote pointson the cathode receive less deposit than generally exposed surfaces. Forexample, in electro-forming a metallic shell about a matrix, ashereinbefore described, it has been found that electro-deposited metaldoes not accumulate readily in areas such as in the corner at Fig. 3).

To correct this deficiency the cathode is raised to the extent that aportion thereof projects above the surface of the electrolyte. Fig. 5illus trates the cathode in its raised position. .Any convenient means,such as a rope 52 connected to a hook secured to the bearing 50, may beThermo-atomlzed metal is then sprayed into the corner 5i.

results have been obtained from a solution com while the cathode isrotated. Means for depositing the therrno-atomized metal. i provided inthe form of a conventional apparatus 54 capable of generating anddepositing fine particles of a such as iron in desired areas of themotel shell. "lhus, electro-iotmed metal and thermom atomized metel ereeo-orciineted in such'e way that the thin portions. of theelectro-formed shell are effectively built up as by forming e, filletthereet. It has been found that when a tietleienes; is so corrected thesupplementary motel end the electro-deposited metal form a homoge= neousstructure.

Toe current between. the terminals 23 and having oeeii maintained for esuficient period, to deposit of lerrous metal is formed on thec'etliotle preferably to on average depth of epproximetely inch, to formto shell 55 (Fig. 6). After the clepositiori is completed the shell maybe seperates: from the matrix El and back plate 6 by heating theassembly in em. oven to approximate i Bill? Fehrenlielt, at whichtemperature the rubber is readily pulled away from the shell, Thisheating also has an annealing effect which increases the tensilestrength of the electro formed metal end renders it more suitable formachine operations.

The shell 55,11EW1X1E been segregated, as shown in l, is provided withe, metallic backing tie, for uniformly supporting the shell end for pro=vltiirog means for eiiectively securing the shell to an outer casing eloi the finished molell ieetive rigid relationship may he established oetween the outer eesim; till end the electro-formeol shell 55 in anyconventional manner; as. for ex ample, the two mey be appropriatelypositioned in e, eenol mold and melted metal such as eliimi mum eoureelbetween them to occupy fully the intervening speoe; or, e suitable bookmay lee ep= plieci to the shell by embedding the same in e semi mold,then pouring iuscd metal over the so that seiol depositions mes loee'i-sthereof. eiter which the backing can be me eliieeci to at shape thatwill efiectively reglstei with interior of the ties-lite,

As e motiifloetion of this practice, the shell 85 more lee hooked mewith metel applied by atomized-i thermal deposition. The sprayed metalthus depositetl mew lie meohinetl to fit the contour @ii the oil e2:@E'LSZDE 1o ecooitleooe with the method anti apperette moltls oomprlsinee so 'lyte, em enamel" metrizi tot applying en etomizetl.

lip

herein tlesetllletl, etltentot es t apparent, end it is intendedmodifications oi the lJEVElZl withmt'ne scopeolf the exit; i-leving thusdescribed, oil. eleim semi, desire to protect Boy 1. 1m eeloerstus iot'Slot hose lyte, em emuler metris; iii t' exieil replice oi as poeuinstievertical ersioio in the deposition mean for lien upon the matrix, memoto shout its elite flaring; e for epplyime' we etomise motel timingmtetlom of the eleotro tleeositiori for J, mess of at least to portionof ferrous shell, means tot eeloe seioi metrix: eeletlve to the let?deposited on portions there mo'lntelnine' the eleetrolyte e tween 175degrees Feliretl Felireeit outlet:

2. en epperetus 550:: i m molds comprising at ten eo.

etzlei seplioe e gmeumette veitleel immersion the eleotro depositionmetms for termite lip-on tlie meitlm'meems for about its title duringeleetr metal during rotetion of the w the eleotmeieposition for inereesmmess Off at least e portion oi the eleetro fert'ous sheil, meme foretljusteoly oos seiel mettle teletive to the level of the electrolyte sothat depositions mey lee slmoltsiieously deposited on portion thereof,and. meems toe meeting the electrolyte. r

